This application describes the University of California, San Diego (UCSD) Department of Medicine (DOM) HIV/AIDS Clinical Trials Unit (CTU) and two Clinical Research Sites (CRSs), one affiliated with the AIDS Clinical Trials Group (ACTG) Network and one with the HIV Prevention Trials Network (HPTN). The Administrative Core of the CTU will be located at the UCSD Antiviral Research Center on the UCSD Medical Center Hillcrest Campus. The UCSD CTU is affiliated, by invitation, with the proposed ACTG and HPTN Leadership Group applications. The ACTG CRS will conduct therapeutic clinical trials developed by the ACTG, targeting HIV-1-infected adult and older adolescent patients recruited from the San Diego County area, concentrating on studies in the high priority areas of translational research, new antiretroviral drug development, optimizing antiretroviral therapy and the clinical management of HIV-1 disease and its complications and co-infections, pathogenesis and treatment of acute HIV-1 infection and drug resistant HIV-1, and the evaluation of candidate HIV-1 vaccines as immunotherapeutic agents in individuals with chronic established HIV-1 infection. The HPTN CRS will conduct clinical trials developed by the HPTN, targeting predominantly HIV-uninfected but high-risk participants drawn from the San Diego County area, as well as HIV-1-infected patients participating in ACTG therapeutic clinical trials (prevention for positives initiatives) in collaboration with the ACTG. The HPTN CRS will concentrate on studies of antiretroviral treatment of acute HIV-1 infection to reduce transmission in this high-risk population, and of behavioral interventions to reduce transmission of HIV-1 and sexually transmitted infections in both HIV-uninfected and chronically infected individuals and their sexual partners. The CTU will initially devote 75% of its research effort on clinical trials implemented by the ACTG and 25% effort on clinical trials conducted through the HPTN, in order to accommodate the large complement of research participants continuing in ACTG studies through the transition period in year 1. These proportions will shift over time as new protocols are implemented and ongoing protocols are completed. Both CRSs will contribute scientifically to each Network through new investigator-initiated studies proposed in the new grant period in these research priority areas, and will further contribute to Network administrative and scientific leadership for both the ACTG and HPTN. The outcome of the proposed research will contribute substantially to halting the spread of HIV/AIDS and to improving the lives of those already infected with HIV-1. ADMINISTRATIVE COMPONENT: